Low overhead jumbo drill supporting bracket



Feb. 6, 1962 J- J- MOR^CCO Em 3,020,012

LOW OVERHEAD JUMBO DRILL SUPPORTING BRACKET Filed Feb. 27, 1959 6Sheets-Sheet 1 v v V m ATTORNEY R ET AL Feb. 6, 1962 J J MO ^CCO3,020,012

LOW OVERHEAD JUMBO DRILL SUPPORTING BRACKET Filed Feb. 27, 1959 6Sheets-Sheet 2 ATTORNEY 6 Sheets-Sheet 3 J. J. MORACCO 'ETAL LOWOVERHEAD JUMBO DRILL SUPPORTING BRACKET Filed Feb. 27, 1959 Feb. 6, 1962Feb. 6, J- J. MORACCO ILT AL LOW OVERHEAD JUMBO DRILL SUPPORTING BRACKETFiled Feb. 27, 1959 6 Sheets-Sheet 4 Way ML ATTORNEY Feb- 6, 1962 J. J.MoRAcco ETAL 3,020,012

Low OVERHEAD JUMBO DRILL SUPPORTING BRACKET Filed Feb. 27, 1959 6Sheets-Sheet 5 Feb. 6, 1962 J- J- MORACCO ETAL 3,020,012 I Low OVERHEADJUMBO DRILL SUPPORTING BRACKET 27, 1959 6 Sheets-Sheet 6 Filed Feb.

mlm T United States Patent l 3,020,012 LW VERHEAD JUMBO DRILL SUIIGRTINGBRACKET Joseph J. Moracco, Utica, and Chandler L. Bush, BriarcliffManor, NX., assiguors to Chicago Pneumatic Tool Company, New York, N.Y.,a corporation of New Jersey Filed Feb. 27, 1959, Ser. No. 796,071 11Claims. (Cl. 24S- 16) This invention relates to boom supported rockdrill apparatus. It is particularly directed to improvements in the boomof the apparatus whereby the conditions under which the drill may beefficiently operated are materially increased and the work that isaccomplished is substantially multiplied.

Boom supported rock drills have `a base support, such as a rig. Thislocates or maintains the horizontal plane of the boom at a substantialdistance above the ground level. Under such conditions the capacity ofsuch drills is limited when attempting snake hole drilling in closeproximity to the ground level, or when attempting to drill parallel tothe ground and below the horizontal plane of the boom assembly. Wherelow overhead conditions are encountered, limited tilting of the rock,

drill in a vertical plane as well as difficulty in maneuvering of theentire yapparatus further limit 'the capacity of a boom supported orjumbo drill apparatus in eiecting snake hole operations, `and otheroperations near the ground level or in `a horizontal plane below thelevel of the boom.

An object of this invention is to provide new and useful improvements of`a practical nature in boom supported drill apparatus, whereby thecapacity and range of oper-ation of such drills is substantiallyincreased.

A further object of the invention is to provide an improved boomsupported rock ldrill apparatus of a practical nature for elfectingsnake hole operations, and for drilling in upright walls at levelssubstantially parallel to and below the horizontal plane of the boom, aswell as at levels substantially parallel to and in close proximity tothe ground.

A more particular object of the invention is to provide an improved andpractical boom assembly for supporting a rock drill, whereby the lattermay be rolled over or rotated `about the longitudinal axis of the boomfrom one position to a diametiically opposite position, or to anyposition intermediately of such positions.

Another object of the invention is to provide a boom assembly having -ahydraulically powered swivel support for a rock drill, wherebyth'e rockdrill may be ,angularly positioned about the longitudinal `axis of theboom `assembly. l Y

A further object of the inventionV is to provide-ai jumbo rockdrillapparatusv which is particularly su' ed' forlow overhead drillingopeations. Y l

VThe invention further lies in the particular structure and novelarrangement of its various components, aswell as in their cooperativeassociation Ywith one another` to effect the results intended herein.

The foregoing and other objects and advantages of this invention willappear more fully hereinafter from a consideration of the detaileddescription which follows, taken together with the accompanying drawingswherein an embodiment of the invention is illustrated. It is to beexpressly understood, that the drawings are for purposes of illustrationand description, and they are not to be construed as defining the limitsof the invention.

. In the drawings:

FIG. l is a side elevational view of 4a. jumbo rock drill apparatusembodying the invention, Lonly they forward orv f'ice mounting end ofthe tractor support being shown at the right end;

FIGS. 2 and 2A are continuations of one another, and show a sideelevational view of the apparatus, parts being cut away to betterillustrate the association of various components to one another;

FIG. 3 is a plan view of the mounting fork showing its association withthe boom drill assembly;

FIG. 4 is a longitudinal section on a horizontal Plane through the boomassembly, and is directed principally to showing the structure of thehydraulic cylinder;

FIG. 5 is a section on line 5-5 of FIG. 2;

FIG. 6 is a section on line 6 6 of FIG. 2; and

FIG. 7 is a section on line 7--7 of FIG. 2.

In the `accompanying drawings is disclosed a jumbo rock drill apparatuswhich is characterized by among other features a roll-over boomassembly. In general, the apparatus includes (FIGS. l, 2, 2A) aroll-over boom assembly 20 which is supported at its rearend upon avehicle 21, and which supports at its forward end a rock drill assembly22. The boom assembly is pivotally anchored to the vehicle, and isassociated with hydraulically powered lift means 23, in such manner thatit may be selectively pivoted up or down in a vertical plane fromhorizontal. rIhe rock drill assembly 2.2 is swivelled to the boomassembly, whereby it may be rolled over or rotated through an angle of180 degrees about the longitudinal axis of the boom assembly from anupright position in a plane `above the boom assembly as in FIG. l, to`an upside down position in la plane below the boom assembly (brokenline FIG. l); and it may be returned to its upright position through thesame angle of rotation, or it may be locked in any intermediate angularposition in the span of rotation.

The supporting vehicle 21 is here illustrated as a tractor, shownpartially in broken line, preferably of low overall height so that itmay be entered into tunnels having low overhead conditions. The tractorhas a low central base or platform 24 carrying a hydraulic supply system25 which -supplies through conventional hose lines, and an associatedmanually operable flow control unit 30, hydraulic fluid to operatevarious hydraulically powered components of the apparatus. Mounted vuponthe forward end of the platform is a vertical pedestal or 'standard 2.6for supporting the boom assembly. IntegralV with the upper end of thisstandard `is a pair of laterally spaced parallel ears 27 (FIGS. 2A, 4).These extend forwardly, and support between them a horizontal pin 2S. Onthis pin the boom assembly 20 is pivotally anchored at its rear end, andis adapted to pivot kin a vertical plane.

The roll-over boom assembly 20' includes an elongatedV openl endedmainor'outer cylinder or hollow boom `29 (FIGS. 2, 2A, 4). Integral withthis cylinder and extending in longitudinal continuation of the rear endthereof is a pair of laterally spaced parallel ear plates 31 betweenwhich are received the ears 27 of the standard. Ears 31 are pivotallyanchored by means of transverse holes therein upon the pin 28. The Vboomassembly 20 is also supported by means of its outer cylinder 29 on thehydraulically powered lift means 23. The latter includes a hydrauliclift cylinder 32 having a closed rear end which is pivoted on ahorizontal pin 3S supported/between depending ears 39 of a bracket 41.The latter i bracket is fixed to the forward underside area of the outercylinder 29 of the boom assembly. The boom assembly is caused to swingon its pivot pin 28 up or down from horizontal, accordingly as thepiston rod 36 is hydraulically extended from or retracted into the liftcylinder 32.

Slidably entered into the outer cylinder 29 through the forward end ofthe latter is an elongated open ended cylindrical roll-over sleeve 42(FIGS. 2, 2A). This sleeve bears upon the inner wall of the outercylinder and is rotatable relative thereto. The sleeve is shorter thanthe outer cylinder, and is confined therein. The rear end 43 of thesleeve bears against an annular internal shoulder 44 of the outercylinder; and the forward end 45 of the sleeve bears against the innerfiat surface of an external cap plate 46. The latter plate is securedover the front end of the outer cylinder by means of an annular seriesof nuts and bolts 47 which engage an annular marginal area of the capplate with a peripheral end flange 48 of the outer cylinder.

Associated with the forward end of the sleeve for rotation with thelatter as a unit is a mounting fork 49 (FIGS. 1-3) which serves as asupport for the rock drill assembly 22. The mounting fork is removablyfixed to the sleeve as a unit. The mounting fork includes a pair oflaterally aligned plates 51 of right angular configuration, comprising apair of outer arm portions 52 continuing at right angles from a pair ofinner arm portions 53. These plates are held in fixed parallel spacedrelation by means of a transverse cylindrical shaft 54 fixed between theouter forward ends thereof; and by means of a transverse plate 55 fixedbetween the rear ends of the plates. The vertical axis of the outer arms52 of the mounting fork is radial to or perpendicular to thelongitudinal axis of the boom assembly. Extending axially rearward fromthe center of the transverse plate 55 is a trunnion or pin 57 having astub forward end 50 fixed in a complementary center hole of thetransverse plate, and having a peripherial collar or flange 56 abuttingand fixed to the rear of the transverse plate. The iiange 56 defines aradial shoulder about the body of the pin which bears against the outerfiat surface of the cap plate 46. The rear body portion of the pin S7extends with a bearing fit through a complementary axial hole 59 of thecap plate, and continues with a slide fit into the open front end ofsleeve 42 wherein it is locked or fixed fast to the latter.

The means whereby the mounting fork and sleeve are made unitary or fixedtogether includes (FIGS. 2, 3, a pair of diametrically opposedlongitudinal key slots 60 in the sleeve registering with complementaryslots or recesses 61 in the pin. In each pair of registered slots 60, 61is received a complementary key 62. A line of bolts 63 passingtransversely through each key, and threadedly engaged in the solidintermediate body of the pin rigidly secure the pin and the sleevetogether for swivelling or rotation as a unit relative to the outercylinder 29. The keys 62 and the heads of the bolts 63 are confined inthe key slots below the periphery of the sleeve so as not to interferewith rotation of the latter relative to the outer cylinder.A The fiange56 of the pin is relatively thick; it serves to space the rear ends 64of the plates 51 of the mounting fork, as well as the transverse plate55, forwardly and clear of the cap plate 46 so as to avoid interferenceof these elements with projecting portions of the nuts and bolts 47 whenthe mounting fork and the sleeve rotate as a unit relative to the outercylinder 29.

The mounting fork 49, as appears in FIGS. 1 and 2, has a normal uprightposition, wherein the transverse shaft 54 is horizontal and in a planesubstantially above the plane of the outer cylinder of the boom assembly20. The rock drill assembly 22 is mounted centrally upon this shaft. Itincludes a conventional elongated rock drill 65 arranged to be fed inconventional manner along an elongated rock drill slide channel 66 whichis clamped into a saddle 67. The saddle is carried by a chassis or block68 of a drill-positioner unit 69. This block is clamped at its bottomend 71 on shaft 54 for pivotal movement about the latter in a verticalplane. Hydraulically powered means 72 is associated by means of a pistonrod 73 with a crank arm 74 of a crank 75 pinned fast at 76 to shaft S4;and has a hydraulic cylinder 77 pivotally anchored on a horizontal pinat 78 to the block 68. This hydraulically powered means 72 serves tocontrol angular positioning of the block 68 and of the associated rockdrill assembly relative to shaft 54. Block 68 has a normal position atopshaft 54 as indicated in FIGS. 1 and 2, wherein the rock drill assembly22 is maintained in a plane spaced substantially above the boom assembly2% and substantially parallel thereto. The outer arms 52 of the mountingfork 49 extend radially relative to the boom assembly sufficiently tomaintain the rock drill asembly spaced clear of the boom assembly.

Hydraulically powered means (FIGS. 2, 2A, 4) associated with the sleeve42 of the boom assembly is operable to rotate or roll the sleeve throughan angle of 180 degrees relative to the outer cylinder 29 and to returnit through the same angle. As earlier mentioned, the mounting fork 49and the rock drill assembly 22 are adapted to rotate or swivel togetherwith the sleeve 42 as a unit. Accordingly, when the sleeve is rotatedfrom its normal position shown in FIGS. 1 and 2, the rock drill assembly22 which is shown top side up at a level above that of the boom assemblywill be carried with the sleeve through an angle of rotation of 180degrees to a position upside down at a level below that of the boomassembly, as indicated by the broken line in FIGS. 1 and 2.

The hydraulically powered means includes an elongated hydraulic cylinder79 which is axially disposed in sleeve 42 for longitudinal movementrelative to the latter. The cylinder 79 has an operational annularclearance 81 between it and the inner wall of the sleeve to allow slightradial play of the cylinder in its movements. An elongated piston rod 82anchored axially at its forward end to a piston 83 within the hydrauliccylinder 79 extends rearwardly and axially with a non-leak slide fitthrough a closure plug 84 threaded into the rear end of the lattercylinder. The piston rod has a thickened rear end-piece, the rearmostpart of which defines an eye lng S5. The latter extends between the earplates 27 of the standard 26, and is pivotally anchored for movement ina vertical plane upon the pin 28. The forward end of cylinder 79 isclosed by a cylindrical head piece 86 which carries a roll or cam pin 87in a transverse hole thereof. The pin 87 is slidably mounted within thetransverse hole of the head piece 86 and thereby is adapted to rotatewithin the latter. The pin has a horizontal roll axis mutuallyperpendicular to the longitudinal axis of the sleeve 42. This pinprojects (FIGS. l, 2, 2A, 4, 6) at its ends 88 through a pair ofparallel and diametrically opposed spiral or lead slots 89, 90 in thesleeve, and through a pair of parallel and dia metrically opposedlongitudinal slots 91, 92 in the outer cylinder 29. The terminal ends ofthe several slots are in lateral alignment.

The hydraulic cylinder 79 is adapted to be hydraulically moved forwardlyand rearwardly relative to the sleeve so as to carry the cam pin 87longitudinally through the several slots from one end of the latter tothe other. The pin is adapted to roll as it rides through the slots.Cotter pins and end washers 93 prevent lateral escape of the pin. Theend washers conform at their inner surface 40 with the contour of theouter cylinder for easy sliding along the latter. A block portion 94 ofthe end-piece of the piston rod 82 has a pair of radial inlet ports 95,96, connected through hose lines, 97, 98 and through the flow controlunit 30 with the hydraulic supply system 25. Port 95 connects with anannular passage 99 which extends longitudinally through the thick wallof the piston rod S2 and communicates by radial passages 101 with theinterior of the hydraulic cylinder 79 rearwardly of the piston 83.Accordingly, hydraulic fluid entered into port 95 acts upon the rearinner end of the cylinder 79 to drive it axially rearward relative tothe stationary piston`83 and relative to the sleeve 42 to the positionshown in FIG. 4. The other port 96 communicates with a passage 102 whichruns axially through the piston rod and opens at its end into theinterior of cylinder 79 beyond the piston 83, so that hydraulic fluidentered into this port drives the cylinder 79 forwardly relative to thestationary piston 83 and relative to sleeve 42 to the position in FIGS.1, 2, and 2A.

The forward and the rear terminal ends 103, 104 of the several slots 89to 92 are slightly greater in diameter than the ends of the cam pin 8Sto allow free movement of these ends; and are laterally aligned with oneanother on a common axis. The width of the several slots `89 to 92 havea similar relation to the ends of the pin so that the latter may ridefreely along the walls of the slots. The cam pin has a horizontalposition as it is carried through the said slots. It is maintained andguided in this position by the longitudinal slots 91, 92 formed in thenon-rotatable outer cylinder 29. The spiral slots 89, 90 represent anangular travelling distance of 180 degrees through one half of a sinecurve. The spiral slots are elongated and preferably have a low leadangle, so as to enable a relatively long travelling distance for the campin and a consequent gradual rotation of the sleeve through its angle of180 degrees. This structure insures greater support for the sleeve, soas to reduce the strain of the heavy drill apparatus upon the latter,and consequently insures greater control over the roll rate of thesleeve. Here the lead angle of the spiral slots from each terminal endthereof is 23 degrees.

As the cam pin 87 is drawn rearwardly by the hydraulic cylinder 79 fromthe forward ends to the opposite ends of the several slots 89-92, itcooperates with the spiralling walls 10S of the spiral slots toprogressively roll or rotate the sleeve 42 through an angle of 180degrees in one direction as indicated by the arrow in FIGS. 1 and 2; andas the cam pin is returned to its starting forward position, it acts toprogressively return the sleeve to its original position through thesame angle of 180 degrees in the opposite direction. f

The positions of the forward and rear terminal ends, respectively 103,104 of thespiral slots are obviously reversed relative to the side areasof the sleeve 42. For example, the forward end of spiral slot 89 is atthe leftof the sleeve (lookingvforward in FIGS. 2, 2A) and the rear endthereof is at the right; and the lead angles of this slot are belowhorizontal at both ends. Accordingly, as the cam pin is drawnrearwardly, the sleeve 42 and the associated rock drill assembly willnormally roll to the Vleft (arrow in FIGS. 1 and 2); and as the cam pinis pushed forwardly, the vdirection of rotation is reversed. rl`hisnormal direction of rotation may be reversed by sliding out the cam pinangularly reversing the cylinder 79, and then restoring the cam pin.

The hydraulic ow control unit 30, schematically shown 'in FIG. 1,connects supply hose lines to the various hydraulically operatedcomponents of the apparatus. Separate three-positional hand levers L ofwhich one is shown in FIG. 1 are associated with the control unit toeffect hydraulic operation of the related hydraulic devices of theapparatus. The particular lever L that is shown serves the hydrauliccylinder 79. This lever is operable in conventional manner, to regulatehydraulic flow through the inlet ports to the hydraulic cylinder 79. Itis operable to control the movement of the latter so as to cause thesleeve 42 to rotate in one direction, or `the other, or to be restrainedin any selected angular position. The other various hydraulicallyoperated devices of the apparatus are subject to similar control throughthis control unit by means of-other levers L, not shown, so as to movetheir pistons in one direction or another or to restrain them in aselected position.

CII

An elongated U-bar 106 (FIGS. 1, 2, 6 and 7) fixed to each side area ofthe outer cylinder protectively covers over the related longitudinalslot 91 or 92 of the outer cylinder 29 so as to guard against entry ofdirt. The forward end of the U-bar is spaced as at 107 rearwardly of theforward terminal ends of the several slots to permit lateral removal ofthe roll pin for purposes of disassembly.

The boom assembly 20 may also be swung in a horizontal plane. To thisend, the standard 26 defines a sleeve adapted for swivel movement about`a vertical axis defined by an inner fixed post 10S. A hydraulic swingcylinder, not shown, but similar to the left cylinder 32 has ahydraulically powered piston rod pivotally conuected by means of a link110- to a pivot pin 111 carried in side lugs 112 of the forward sidearea of the outer cylinder 29. The opposite end of the swing cylinder ispivot-ally connected in a manner similar to tha-t of the lift cylinder32, to a second vertical swivel standard 26' carried by the tractor inlateral spaced relation to the standard 26.

The roll-over feature of the boom assembly 20 enables the rock drill 65to effect drilling operations over the surface area of an upright wallfrom the top to the bottom of the latterv in planes parallel to theground level. It enables drilling of elongated snake holes in closeproximity to and parallel to the base of a wall. The hydraulic liftmeans 23 enables the boom assembly 20 to be 'pivoted vertically tovarious positions from horizontal, thus also enabling angular holedrilling into upright wall areas.

yThe apparatus described is of particular advantage where low overheadconditions exist, as appears in FIG. l. When the boom and the rock drillassemblies are brought into a parallel Ihorizontal relation, as in FIGS.l and 2, -the overall height of the apparatus is relatively low, thusenabling free movement in a low overhead tunnel. Where tilting of therock drill assembly relative to horizontal is difficult because of lowoverhead conditions, the roll-over boom yassembly 20 will neverthelessenable drilling operations to be made over the upper and lower areas ofthe upright wall 113, above and below the horizontal of the boomassembly and also in close proximity to the door 114 of the tunnel.

While an embodiment of the invention has been illustrated and describedin detail, it is to be expressly understood that the invention is notlimited thereto. Various changes might be made in the design andarrangement of the parts without departing from the spirit and scope ofthe invention; and it is our intent, therefore, to claim the inventionnot only as-shown and described but also in all such forms andmodifications thereof as may reasonably be construed to fall within thespirit of the invention and the scope of the appended claims.

What is claimed is: v

1. A boom assembly for rock d n'll apparatus comprising a support, anouter cylinder having in diametrically opposed wa-ll areas thereof apair of elongated longitudinally extending parallel slots and anchoredat its rear end to the support; an elongated sleeve disposed in thecylinder for rotation relative to the latter and having in opposed wallareas thereof a pair of spiral slots the terminal ends of which areregistered with corresponding terminal ends of the parallel slots; meansconfining the sleeve within the cylinder against endwise movementrelative to the latter, a hydraulic cylinder disposed within the sleeveland laxially movable relative to the latter and relative to the outercylinder, the hydraulic cylinder having a forward and a rear head; atransverse pin carried in the forward head of the hydraulic cylinder formovement with the latter and projecting slidably at its ends through thespiral slots and through the longitudinal slots; a piston within thehydraulic cylinder having a piston rod projecting through the rear headof the hydraulic cylinder' anchored at its free end to the support; andwalls in the spiral slots cooperable with the ends of the pin upon axialmovement of the latter as a consequence of axial movement of thehydraulic cylinder so as to cam the sleeve angularly relative to theouter cylinder; and external drill mounting means having an axialconnection with the sleeve for angular movement with the latter as aunit and having a radial end arm adapted to support a drill nicmber.

2. A boom assembly as defined in claim l, wherein the piston rod hasadjacent to its rear end a pair of inlet ports, one having a passageextending through the rod and opening into the hydrauliccylinderforwardly of the piston so as to communicate hydraulic operatingduid to the hydraulic cylinder forwardly of the piston and the otherhaving a passage extending through the rod and opening into thehydraulic cylinder rearwardly of the piston so as to communicatehydraulic operating tiuid to the hydraulic cylinder rearwardly of thepiston.

3. A boom assembly as defined in claim l, wherein the outer cylinder ispivotally anchored at its rear end to the support for pivotal movementin a vertical plane, and the boom assembly having hydraulic lift meansfor effecting said pivotal movement.

4. A boom assembly as in claim l, wherein each spiral slot extends aboutopposed areas of the sleeve for an angular distance of 180 degrees.

5. A boom assembly as in claim 4, wherein the lead angles of the spiralslots are relatively low, lead in one direction at one end of thesleeve, and lead in the opposite direction at the other end of thesleeve.

6. A boom assembly as dened in claim l, wherein the external mountingmeans is of right angular contiguration having a rearwardly extendingarm axially connected with the sleeve and having its other arm definingthe said radial end arm adapted to support the drill member.

7. A boom assembly as dened in claim 6, wherein the external mountingmeans is removably locked to the sleeve by means including a rear axialpin extending slidably into the sleeve, key means received incomplementary slots of the sleeve and pin, and fasteners transversely ofthe pin and key means securing the key means in the slots.

8. A boom assembly as defined in claim 6, wherein a cylindrical shaft istransversely supported by the radial cud arm, and saddle means adaptedto support the drill member is pivotally supported upon the shaft.

9. In rock drill apparatus, a support, an elongated cylhavinglongitudinal movement in the slot means relative to the boom andcylinder and cooperable with the slot means to translate such pinmovement into rotary movement of the cylinder about the longitudinalaxis of the boom, and hydraulic piston means for giving saidlongitudinal movement to the pin means.

10. ln roel; drill apparatus a support, an elongated hollow boom open inits forward end, means mounting the boom at its rear to the support andpreventing rotation of the boom relative to the support, a roel: drillmountY disposed externally of the forward end of the boom including anelongated cylinder' disposed in the open forward end of the boom forrotation about the longitudinal axis of the latter, means confining thecylinder within the boom against endwise movement relative to thelatter, spiral slot means in the cylinder, straight slot means in theboom, hydraulically movable cam pin means disposed transversely of thespiral and straight slot means having movement longitudinally of thespiral and the straight slot means and cooperable with the spiral andthe straight slot means in its movement for imparting rotary motion tothe cylinder relative to the boom.

ll. A boom assembly for rock drill apparatus comprising a support, anouter cylinder having in diametrically opposed wall areas thereof a pairof elongated longitudinally extending parallel slots and anchored at itsrear end to the support; an elongated sleeve disposed in the cylinderfor rotation relative to the latter and having in opposed wall areasthereof a pair of spiral slots the terminal ends of which are registeredwith corresponding terminal ends of the parallel slots; a hydrauliccylinder disposed within the sleeve and axially movable relative to thelatter and relative to the outer cylinder, the hydraulic cylinder havinga forward and a rear head; a transverse pin carried in the forward headof the hydraulic cylinder for movement with the latter and projectingslidably at its ends through the spiral slots and through thelongitudinal slots; a piston within the hydraulic cylinder having apiston rod projecting through the rear head of the hydraulic cylinderanchored at its free end to the support; and walls in the spiral slotscooperable with the ends of the pin upon axial movement of the latter asa consequence of axial movement of the hydraulic cylinder so as to camthe sleeve angularly relative to the outer cylinder; and external drillmounting means having an axial connection with the sleeve for angularmovement with the latter as a unit and having a radial end arm adaptedto support a drill member; wherein the outer cylinder has a cap platebearing against a forward end of thc sleeve and has an internal shoulderbearing against the rear end of the sleeve whereby the sleeve isconfined in the outer cylinder against endwise movement.

References Cited in the file of this patent UNITED STATES PATENTS2,218,491 Osgood Oct. l5, 1940 2,532,079 Beltz Nov. 28, 1950 2,586,773Ball Feb. 26, 1952 2,867,412 Hurd Ian. 6, 1959

